Micro-mirrors are frequently used for image projection, whereby, for example, laser beams in bundled form strike a biaxially suspended micro-mirror and are deflected by same onto a projection surface. An image may be rasterized on the projection surface by synchronizing the intensity modulation and optionally the color modulation of the laser beam with the motions of the micro-mirror.
The control is carried out in such a way that the micro-mirror is tilted horizontally and vertically, so that an image is built up line by line. After each image line the tilt of the vertical axis may, for example, be slightly increased so that the individual image lines are projected, one below the other, on the projection surface. This process may be iterated at an image refresh rate of greater than 50 Hz, thus giving the observer the impression of a stationary image, or optionally a sequence of moving images.
The micro-mirror may be tilted with the aid of actuating elements, whereby a mechanical, electrostatic, magnetic force or a force generated in some other way is selectively exerted on a plurality of actuating elements in order to deflect the micro-mirror with respect to one or both of the tilt axes of the micro-mirror. As a result of the micro-mirror being in almost constant motion due to the image build-up pixel by pixel, a high energy level is necessary to actuate the actuating elements. In particular when these types of image projection systems are used in devices having a limited power supply, for example in portable electronic devices having accumulators as a power source, it is desirable to minimize the energy consumption resulting from the control of micro-mirrors in order to prolong the operating time of the devices.
The publication U.S. Pat. No. 7,515,329 B2 discusses, for example, methods for the resonant control of MEMS mirrors, using control signals which are subdivided on two mirror axes.